Isomerization of paraffins



H. PINES ET AL ISOMERIZATION OF PARAFFINS Filed Oct. 12, 1940 Oct. 27, 1942.

FRACTlONATOR- REACTOR 2 12; I3: 514 15 ige 1 a 9 IO W INVENTORS u HERMAN PINES JYHERMN s. BLOCH I I I 1 I ATTORNEY Patented Oct. 27, 1942 "UNITED STATES PATENT OFFICE" Herman Pines and Herman S.

111., assignors to Universal Oil Bloch, Chicago,

Products Comv pany, Chicago, 111., a corporation of Delaware I Application October 12, 1940, Serial No. 360,906

6 Claims. (01.260-676) L,

This invention relates to the treatment of paraffln hydrocarbons of normal or mildlybranched chain structure.

In a more specific sense the invention is concerned with a process whereby normal or mildlybranched chain paraflln hydrocarbons are converted into isoparafiin or more-branched chain parafiin hydrocarbons, the process involving the use of special catalysts and particular conditions of operation which favor the isomerization reactions so that relatively high yields of the iso or more branched chain compounds are produced.

chain parafiin, hydrocarbons from the corresponding less-branched chain liquid parafiins is desirable because of the generally higher antiknock value of the iso compounds. Furthermore, the branched chain parafi'ins, both gaseous and liquid being generally more reactive than the corresponding normal hydrocarbons, may be utilized in the production of other branched chain paraffins, byso-called alkylation reactions in the presence of suitable catalysts. Also, lower boiling isoparaflins, such as isobutane and isopentane, may be dehydrogenated to the corresponding branched chain olefins, which, are utilizable for the production of high quality aviation gasoline, by a combination of catalytic polymerization followed by hydrogenation of the polymers, producing parafiinic motor fuel.

In one specificembodiment the present invention comprises a process for isomerizing a normal paraflin hydrocarbon which comprises subjecting said normal paraflin hydrocarbon to contact with a supported aluminum chloride-containing catalyst to form-an isomerization product containing a substantial proportion of more-branched chain paraffin hydrocarbons; separating said product into an isomerization mixture comprising essentially unconverted normal parafiln and morebranched chain parafiin hydrocarbons and a gas mixture comprisingessentially hydrogen; hydrogen chloride, ethane, and methane; subjecting parafilns by a treatment similar to that set forth ture; and recycling said unconverted normal paraflln hydrocarbon to further isomerization treatment.

In a further embodiment the present'invention comprises the isomerization of mildly-branched chain paraifins into more-highly branched chain for isomerizing a normal paraflin hydrocarbon.

' The formation of the 'iso or more-branched Normal paraffin hydrocarbons with which the process of the present invention is concerned may be either normally gaseous orliquid.- Normal butane,which constitutes the gaseous normal paraflin-which may be isomerized by the process of this invention, is produced in considerable quantities in the oil refining industry. -Both normal butane and isobutane occur in substantial amounts in natural gases (in which the normal compound usually predominates), in refinery gases which are evolved from crude petroleum storage tanks, and in the primarydistillation of crudes; and they are also present in considerable percentages in the gases produced incidental to v the normal compound is the cracking of heavy petroleum fractions for the production of gasoline. In the case of cracked gas mixtures, the relative proportions of iso and normal butanes vary, but the ratio of the iso to as a rule considerably higher than in natural gas.

Butanes may be considered as more or less marginal compounds in respect to their desirability in ordinary gasoline, that is, a certain per centage of them is essential for suflicient vapor pressure to insure ease in starting, while anexcess tends to produce vapor lock. For these reasons the total percentage of 4-carbon atom hydrocarbons-iscommonly adjusted in conjunction with the boiling range and vapor pressure of the other chain parailins, and a higher boiling paraflin mixgasoline components to produce a gasoline of de- 1 sirable starting characteristics according to sea- I sonal demands.

The butanes at the present time bear a further important relationship to oil refining in that their excess production is beingutilized as a source of gasoline either by ordinary thermal cracking or by special catalytic dehydrogenation processes followed by polymerizationin which catalysts may or may not be used. Investigations have shown that isobutane is considerably more amenable to cracking and dehydrogenation, both with and without catalysts, than the normal compound. Considering the corresponding mono-olefins, the normal butenes are considerably more diflicult to polymerize, either thermally or catalytically, than isobutene, and it is found, also that the octenes representing the dimers of isobutene are of higher antiknock .value from normal butenes, which holds also for the octanes pro- ,duced by hydrogenation. It is, therefore, of considerable importance at the present time to con vert as much as possible of the normal butane production into isobutane.

Liquid normal paraflins are produced in considerable quantities in the oil refining industry.

They 'occur in substantial .amounts in natural gasolines, in the higher boiling constituents of natural gas commonly known as casing head gasoline, and in gasolines produced in relatively lyst.

high yields by the cracking of relatively heavy -petroleum fractions. In the case of cracked gasolines, the relative proportions of iso and normal parafllns vary. I

Materials suitable for use as paraffin isomer- .izin'g catalysts comprise substantially anhydrous aluminum chloride alone'or in admixture with vrelatively smaller proportions of a chloride of a metal selected from those. of iron, zinc, copper, and others. The aluminum chloride or metal halide mixture may be used either as such or supported upon, a substantially inert carrier selected from thegroup consisting of activatedcarbon, pumice fuller's earth, raw and acidtreated clays, .diatomaceous earth, celite, unglazed porcelain, crushed flrebrick, a silica-alumina composite, etc. q

The term activated carbon as used in the present specification and claims is intended to include any type of prepared carbon or carproceeds more or less in one direction until an equilibrium is established.

Experiments-have indicated that good results are obtained in paraiiln isomerizations when from about 0.5% to about by weight of hydrogen chloride is present in the reaction mixture. This amount of hydrogen chloride may be introduced directly, as such or as a solution in butane, or partly produced in situ by using amounts of water or steam which cause a certain amount of hydrolysis of the metal chloride cata- While inert gases such as'nitrogen may be employed alternatively for imposing the desired pressure, experiments have shown that hydrogen is preferable .as its presence seems to minimize undesirable side reactions involving decomposition rather than the desired isomerization.

An essential feature ofthe present invention is the'combination of steps employed for separating hydrogen chloride from the isomerization products and from the relatively small amounts of accompanying decomposition products and for recovering said hydrogen chloride in suitable form for recycling to further use in the isomerization of more of the normal or mildly branched chain paramnic material charged. This recovery ofphydrogen chloride is accomplished, as will be described subsequently in more detail, by passing a mixture oflight gaseous products of the process comprising essentially hydrogen chloride hydrogen, ethane, and

bonaceous material which is more orless granular and possessedof good porosity and structural strength and which has been prepared by general steps involving the leaching of adsorbed materials from granular residual carbonaceous materials such as woodchar and various varieties of coke by mineral acids and by the controlled heating. preferably under vacuum, to ex pel adsorbedliquids and gases. It is recognized that various-forms of active granular chars .will vary considerably in adsorptive capacity so that therefore the properties of catalysts prepared when using them in accordance with the present invention will vary both in respect to the amount of aluminum absorb and-in respect to the periods of service in which they are able to maintain a practical activity in different organic reactions.

,While these catalyst-forming materials may a be used more or less interchangeably, some are more eflicient' than others and it is not intended to'imply that they are definitely equivalent.

Also it frequently happens that one type of carrier or support is better for use with a given metal halide catalyst, depending'upon-the ratio of the metal halide to support found experimentally to be best for the furtherance .of the paraiiin-isomerizing reaction.

In the presence of a compomte catalyst such as those hereinabove set forth, the paraffin hydrocarbon charged-may be converted chloride which 'they are able to has been-calcined at a eliminate a highproportion of moisture. Suitmethane through an adsorber containing a suitable -granular solid maintained at some temperature within the approximate limits of 0 and 210 F.and under a pressure between about 500 and about 2000 pounds per square inch for adsorption of hydrogen chloride. lar solid adsorbents may stances as dry charcoal of either animal or vegetable origin, similar activated chars derived from petroleum coke,-- calcined activated alumina, calcined silica gel, calcined diatonraceous earth, or any active and porous earth or clay which temperaturesuiiicient to Suitable granuable adsorbents have some selectivity in adsorbing hydrogen chloride preferentially to methane or ethane which may also be present inthe lighter fraction of the isomerization products derived from isomerization of paraiiins in the presence of hydrogen'chloride and an aluminum chloride previously adsorbed by the granular ad-.

sorbent contained therein. Such removal frominto ap-rpro ximateiy 30-60% or more of more-highly branched chain paraiiins while utilizing a cata-' lyst-temperaturewithin the approidmate limits of and 650' I. and under a pressure of from substantially atmospheric to approximately '3000 pounds per square inch. Evidently the use of superatmospheric pressure diminishes the vol I atilisation of aluminum chloride-from'the cata- 11st 'and also tends to depress undesirable side reactions which would result in the formation of hydrogen and of relativelylow molecular weight hydrocarbons so that the desired isomerization phere.

chloride-containing catalyst.

It is preferable to utilize actorsfor efiecting such an adsorptive removal of hydrogen chloride in order that while one reactoris in use for adsorption purposes, the

other may be treated; for recovery of hydrogen an adsorbent of adsorbed hydrogen chloride may be termed desorption. Desorptionmay be accompiished either by raising the temperature grammatically means embodying a typical proccomprise such subtwo or more reillustrating the cooperative I ess flow for isomerizing a normal or mildlythe isomerization of any particular paraflinic hydrocarbon.

Referring to the drawing, normal butane may be introduced through line I containing valve 2 to pump of compressor 3 ,which discharges through line 4 containing valve 5. Simultaneously hydrogen may be introduced through line 6 containing valve 1 to compressor 8 which discharges through line 9 and valve l0 into line 4, already mentioned, while hydrogen chloride may be admitted through line H containing valve l2 to compressor l3 which'discharges through line l4 and valve 15- to line [through which the commingled mixture oi! normal butane, hydrogen, and hydrogen chloride may be conducted to .isomerizing reactor 16, although more than one .isomerizing reactor may be employed, if desired.

v mains adsorbed by the granular filler in adsorber Alternatively hydrogen chloride may becharged in the form of a solution in n-butane, if desired,

or it may be introduced under pressure from any suitable source. 'Isomerizing reactor l6 may consist of a chamber containing a granular catalyst comprising essentially aluminum chloride or a mixture of aluminum chloride and another metal halide deposited upon a.substantially inert carrier such as described previously in this specification. This isomerizing treatment may be cit-- .fected at a temperature within the approximate limits of 100 and 650 F. under a pressure at some point in the range of substantially atmospheric to approximately 3000 pounds per square inch.

Thus isomerizing reactor I may contain a. granular catalytic material which isrelatively non-volatile under the conditions of use and which in the presence of hydrogen chloride is capable of producing a substantial degree of isomerization of normal butane to isobutane.

From reactor, l6. a mixture comprising essentially isobutane, unconverted normal butane, hy-

drogen, hydrogen chloride, and arelatively small amount of decomposition products including propane and lighter hydrocarbons maylbe conduct ed through line H and valve l8 to-iractionator IQ of conventional design to separate therefrom,

a fraction comprising essentially ethane and lighter gases, isobutane alone or admixed with a relatively small amount of propane normal butane, and a mixture of pentanes and higher hydrocarbons. ,Saidisobutane, or isobutane mixed with small amounts'pr propane, may be withdrawn from iractionator 19 through line 20 containing valve 21' to cooling and storage, not shownin the diagrammatic drawing. Normal butane separated in iractionator 18. may be conducted therefrom through line 22 and valve 23 05.

to pumpor compressor 24 which discharges through line-25 and valve into line'4, already mentioned, through which normal butane is being conducted tozisomerization. Pentanes and higher hydrocarbons may be withdrawnirom the lower portion of iractionator l9..through line 21 k and valve 28 to storage,

Light gases comprising essentially hydrogen,

hydrogen chloride, ethane, and methane may be For convenience in 5 through line 29 and valve 30 to compressor 3| which discharges through line 32 through branch line 35 and valve 36 to adsorber. The adsorbers may be cooled by means not. shown to maintain a temperature between about 0 and about 210 1", while they are operated under a pressure within the approximate range of 500 to 2000 pounds per square inch.

The adsorption system comprises at least two units suchas adsorbers 34 and '31 although a largeri number may be employed if desired and either single or multiple units may be used in conjunction with each other. .The adsorbers are so arranged that one may be in use for adsorbing hydrogen chloride from said light gases while the other'is being desorbed of hydrogen chloride which has accumulated upon the adsorbent in a prior adsorbing treatment of the eifluent light gases. Thus if the light gases from fractionator 0 l9 are being pumped into adsorber 31, valves 33, 39, and 45 are shut so that the gases pass through l ne 35 and valve 36 into adsorber 31 andirom v thence the hydrogen chloride-free gases pass through lines 38 and 40 and valve 4! to waste or toother use while the hydrogen chloride resuiliciently from the adsorbent in adsorber 34 and the adsorbent in adsorber 31 has become substantially saturated with hydrogen chloride,

valves 36,-, and 45 are shut and valves 33, 39 and 45 are opened, adsorber 34 thereafter being used for treating the light gases and hydrogen chloride being desorbed from the adsorbent in adsorber SI-and then pumped by pump 46 andrecycled to isomerizing reactor Hi. If desired thedesorption may be efiected by increasing the temperature of the chamber containing the adsorbent without substantial-lowering of pressure or by simultaneous increasing the temperature and lowering the pressure as desired.-

The following-example is introduced to show results normally expected in the operation of the 4 process, although with no intention of unduly limiting the generally broad scope of the invenonz- A- mixture containing 84.5 molecular proportions of normal butane,.l2.4 molecular, proportions of anhydrous hydrogen chloridaand 3.1 molecular proportions of hydrogen is passed at 390 F. under a pressure or 650 pounds per square nch through a reactor containing a-composite of 3'Z-.6%' byweight of substantiailyanhydrous aluminum chloride and 62.4% by weight of activategl cocoanut charcoal in the form of 4- -l0 mesh granules. When the n rmal butane is charged as liquidat a rate gorres onding to a liquid spacevelocity of l, the reaction products consist, of

hydrogen and hydrogen 'chloride originally;

charged and a hydrocarbon mixture comprising essentially 0.4% by volume of methane, 0.2% ethane, 2.3% propane, 46.0% isobutan'e; 49.4% unconverted normal butane, and 1.1% pentane. Fractional distillation of saidreaction product substantially separates propane, and higher hydirected fro near the top" of iractionator l9 drocarbons from a lig 8 mixture wi h anmixture with-a solid adsorbent to separate hydro- .gen chloride from the mixture by adsorption I proximately the following volume per cent com-.

position: methane, 2.0%; ethane, 1.0%; propane,

1.5%; hydrogen, 19.2%; and hydrogen chloride; v

During passage of said light gas mixture 5.

through activated cocoa nut charcoal at an hourly rate corresponding to a gaseous space velocity of Y 2000 at 175 F. under a pressure of 700 pounds per square inch, approximately 95% of thehydrogen chloride-is adsorbed therefrom by the charcoal.-

After passage of approximately 1000 volumes of said light gasmixture through 1 volume or adsorbent, the removal of hydrogen chloride becomes less complete. The stream oisaid light gas mixture is then stopped,the pressure is re-f duced to atmospheric, and then the adsorber is Y evacuated to a pressure of approximately 0.1 atmosphere. The hydrogen chloride-containin gas mixture recovered during said evacuation conrams 90-95% or hydrogen chloride mixed with relatively minor proportions of hydrogen, meth ane,- ethane, and propane I Hydrogen chloride-containing gas recovered as hereinabove set forth is'suitable for commingling with normal butane being charged to contact with the aluminum chloride charcoal isomerizing catalyst. v

The character of the present invention and particularly its commercial'value are evi ent from the foregoing speciflcationand exampleralthough 3.0

the proper scope of the invention is not limited to exactcorrespondence with the descriptive and numerical material presented. a

We claim as our invention:

, 1. In the isomerization of remains in the pres- 5 ence 'of hydrogen chloride and an isomerizing catalyst comprising substantially anhydrous aluminum chloride, the method which comprises separating from the products of the isomerizingstep an isomerized paraflinic traction, unconverted p'araiilnic hydrocarbons and a gas mixture containing hydrogen chloride. contacting said gas thereof in the solid adsorbent. subsequently desorbing hydrogen chloride from the solid adsorbeat and supplying the same to the isomerizing verted paraflinic hydrocarbons and a gas mixture containing hydrogen chloride, contacting said gas mixture with a .solid'adsorbent to separate hyrogen chloride from the mixture' by adsorption thereot'in the solid adsorbent, subsequently desorbing hydrogen chloridefrom the solid adsorbent and ommingling the samewith said unconverted l ramnic hydrocarbons, and supplying the resultant mixture to the isomerizing step.

3. The method as defined in claiml further "characterized in that the gas mixture is contacted with the solid. adsorbent at a temperature in the approximate range of 0 F. to 210 F. and under apressure between about 500 and about 2000 pounds per square inch, andin that the adsorbent is desorbed at a temperature between about F. and about 500 F. under a lower pressure than is maintained during the contacting step. I

4. The method as defined in claim 1' further characterized in that. the solid adsorbent comprises activated carbon. 5. The method defined in claim 1 further characterized in that the paraflins undergoing isomerization comprise normal butane.

6. The method as defi ned in claim 1 further characterized in that the paraflins undergoing isomerization comprise normal pentane.

HERMAN PINES.

. HERMAN s. BLOCH. 

